This invention relates to disposable electrochemical sensors of the type used for quantitative analysis, for example, of glucose levels in blood, for pH measurement, or the like. More particularly the invention relates to means for electrical connection of such sensors to a measuring apparatus.
U.S. Pat. No. 5,437,999 discloses an electrochemical sensor of the kind which in use is electrically connected with a power source. The sensor is constructed from two spaced apart printed circuit boards each having a metal layer on one side and disposed so that the metal layers are facing each other in spaced apart relationship. The metal layers are photolithographically treated to define electrode areas which form part of a cell. At one end of the assembly the electrode substrates are cut to provide laterally spaced protruding tabs bearing the metal layer. The exposed metal surfaces of the tabs act as contact pads, each contact pad being electrically connected with a corresponding electrode. The contact pads in turn engage contact prongs connected to a power source and provide electrical connection between the sensor and a power source.
The arrangement of U.S. Pat. No. 5,437,999 suffers from the disadvantages that the substrate is required to be of considerable rigidity in order to ensure satisfactory and reliable electrical contact. Moreover the user is often left uncertain as to whether a sensor has satisfactorily been connected with the power source.
In co-pending applications PCT/AU96/00207, PCT/AU96/00365, PCT/AU96/00723 and PCT/AU96/00724 there are described various very thin electrochemical cells. Each cell is defined between facing spaced apart electrodes which are formed as thin metal coatings (for example sputter coatings) deposited on thin inert plastic film (for example 100 micron thick PET). The electrodes are separated one from the other by a spacer of thickness of for example 500 xcexcm or less.
The connection arrangement of U.S. Pat. No. 5,437,999 is not suitable for use with the extremely thin sensor devices of the kind discussed in our co-pending applications in view of the flexibility of the insulating electrode carriers. In general, it is desirable that the disposable sensor be capable of simple, quick, reliable and effective connection with the power source in the measuring device by unskilled users. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
According to a first aspect, the invention provides a sensor adapted for electrical connection with a power source having first contact means, the sensor comprising:
a first insulating substrate carrying a first electrode and a second insulating substrate carrying a second electrode, said electrodes being disposed to face each other in spaced apart relationship,
a first cut-out portion extending through said first insulating substrate and a spacer to expose a first contact area on the second insulating substrate to permit a first contact means to effect electrical connection with the first contact area disposed on the second insulating substrate, the first contact area being in electrically conductive connection with the second electrode.
The first contact area may be maintained at a predetermined depth from the first insulating substrate.
According to a second aspect, the invention provides a sensor according to the first aspect further comprising a second cut-out portion extending through said second insulating substrate and the, or another, spacer to expose a second contact area on the first insulating substrate to permit a second contact means to effect electrical connection with a second contact area disposed on the first insulating substrate, the second contact area being in electrically conductive connection with the first electrode.
The second contact area may be maintained at a predetermined depth from the second insulating substrate.
According to a third aspect, the invention also provides a sensing system comprising a sensor according to the first or second aspects and a sensing apparatus including a first contact means and/or second contact means adapted to effect electrical contact with the first and second contact areas respectively.
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In preferred embodiments the insulating substrate is made of a flexible insulating material. The second electrode and the first contact area are formed from a unified layer of metal deposited on the first substrate, and more preferably deposited by being sputter coated thereon. Suitable metals include, but are not limited to palladium, gold, platinum, iridium, and silver. Carbon may also be used. Desirably the contactor is a metal contactor which is resiliently biased to extend through the first cut-out portion to make contact with the metal first contact area on the second substrate. In highly preferred embodiments the contactor is adapted for click engagement with the cut-out portion which extends through the first insulating substrate and the spacer.
With a connector according to the current invention the spacer layer provides extra strength. A rigid connector can therefore be formed using flexible materials. This allows a wider range of materials to be utilized. An audible confirmation of connection can also be simply provided by the current invention unlike the connector described in U.S. Pat. No. 5,437,999.